SPI to the SD card specifications

[uminded]

According to schematic, the SDCard is attached in QIO mode, but we still need to figure out if software use it that way.

I'm quite busy the next few weeks but I may dig through the curated linux kernel modules and figure out how they are running the SD card. QSPI is pretty standard and given the specs say they support 256gig cards I imagine its QSPI >60MHZ for a minimum 15mb/s transfer rate. Theoretically, you can run a QSPI at 100MHZ with quad data rate to achieve 100mb/s throughput sans error checking.